Coated surfaces for moving stairways



Aug. 11, 1964 A. FABULA 3,144,118

COATED sURFACEs FOR MOVING sTARwAYs Filed Jan'. 14. 1960 4ms/@Ew Fnsi/LnINVE NTOR Y ATTORNEY United States Patent O 3,144,118 CUATED SURFACESFOR MOVING STAIRWAYS Andrew Fabula, Hohokus, NJ., assignor to OtisElevator Company, New York, N.Y., a corporation of New Jersey Filed Jan.14, 1960, Ser. No. 2,448 7 Claims. (Cl. 198-16) The invention relates tomoving stairways and more particularly to the arrangement of suchstructures as to enhance the safety of users of them.

This application is a continuation-in-part of my copending applicationSerial No. 753,439, filed August 6, 1958, now abandoned.

Moving stairways comprise an endless series of steps which are movedbetween balustrades from one landing to another for the purpose ofconveying passengers. Each step includes a tread plate, disposedsubstantially horizontally for carrying passengers, and a verticallydisposed riser. The steps emerge from underneath the landing at theentrance of the stairway in platform formation, transfer to stepformation on the incline of the stairway and change back again toplatform formation to pass underneath the landing at the exit end of thestairway. An endless handrail is supported by the balustrade on eachside of the stairway and is driven in synchronism with the steps.

Passengers through misuse of the moving stairway sometimes create ahazard to themselves and their clothing. Such a hazard is created when,while the stairway is in operation, a high frictional object isimproperly placed in simultaneous contact with opposing surfaces ofrelatively moving adjacent stairway parts, between which a commonoperating clearance space is necessarily provided. This is especiallytrue of rubber overshoes and sneakers, since both are made of exiblematerial having a relatively high coefficient of friction, whichmaterial may be readily pinched and drawn into a common clearance space.However, the relative motion between such adjacent parts to bedangerous, must be in a direction which effectively tends to draw suchobjects into the operating clearance space common to such adjacentparts. Such relative motion occurs between the side edges of the treadplate and riser of each step and the stationary adjacent sides of thebalustrades, and, as the steps change from step formation to platformformation at their exit end, between the outer surface of the riser ofeach step and the adjacent edge of the tread plate of the adjacent step.

As an example of such dangerous misuse of a moving stairway, it hashappened that a child, wearing sneakers and riding a descendingstairway, improperly has faced backwards and placed the toe of onesneaker into the corner formed by the riser of the succeeding,descending step and the stationary side of the adjacent balustrade.Since the toe and that riser move downward along the incline relative tothe adjacent balustrade surface, frictional engagement between thebalustrade surface and the sneaker is sometimes sufficient to draw thesneaker upward into the clearance space necessarily provided between theedge of the riser and the adjacent balustrade. In such a case, thesneaker is pinched and wedged into that space and damaged. Unhappily,sometimes the childs toes are also injured, being mashed or bruised bythe relatively moving parts. The injury is usually more severe when,with the sneaker thus caught between the riser edge and the adjacentbalustrade, the stairway changes from step to platform formation at itsexit end. This is so, since at that point the riser moves downwardrelative to the step tread upon which the child is standing, therebyintensifying the pinching and wedging of the captive sneaker toe. IneXtreme cases, the captive sneaker and foot are carried along to thepoint where the stairway disappears underneath the landing platform andare there amputated.

Attempts to remove such hazards have been made in the past, such as, forexample, by minimizing the width of these clearance spaces. Suchattempts have been effective to prevent relatively large objects frombeing wedged into the clearance spaces but have not had the desiredelect of preventing high frictional and iiexible objects from beingpinched and wedged into such crevices.

Also, in some installations, a handrail is positioned relatively closeto a stair well wall and objects may become wedged between the side edgeof the moving handrail and the adjacent stair well wall and be damagedby relative motion between the two. The handrail surfaces are purposelymade of a material having a relatively high coefficient of friction(such as rubber, so that a passenger may easily maintain a grip on thehandrail) and the adjacent wall surface is also usually of roughmaterial. In such installations, as the handrail moves relative to theadjoining stair well wall, an object which is touching that wall andalso resting against the handrail side edge which faces that wall may,under certain circumstances, become frictionally engaged suiiiciently byboth. surfaces to be wedged in between the two and crushed. Thisoccasionally happens to packages improperly placed on the handrail bypassengers or to the forearms of small children who, while riding on themoving stairway, foolishly attempt to slide their hands along theadjoining wall surface in advance of the handrail travel or place theirforearms between the wall and handrail. In these latter instances thechilds small arm becomes wedged between the relatively rough surface ofthe wall and the handrail. The moving handrail, which tends to move thearm forward, causes it to be so twisted as to fracture it in the area ofthe wrist.

An object of the invention is to make moving stairways safer forpassengers, their clothing and objects carried by them.

It is another object of the invention to minimize the effectivefrictional forces tending to draw objects into the operating clearancespaces provided between passenger carrying components of movingstairways and adjacent parts which are in relative motion with respectto such passenger carrying components.

The invention involves eliminating potential hazards to moving stairwaypassengers, their clothing and objects carried by them under conditionswhere such hazards are due to relative motion between two stairwaycomponents with which a passenger, his clothing or an object beingcarried is improperly in simultaneous contact with. This is accomplishedby substantially reducing the coeflicient of friction of the contactingsurface of one of the co4 operating components without reducing thefrictional engagement between the passenger and the moving stairwaynecessary for safe passenger transfer from one landing to another.

Features and advantages of the invention will be seen from the above andfrom the following description of the preferred embodiment whenconsidered in conjunction with the drawings and appended claims.

In the drawings:

FIGURE l is a perspective partial view of the lower end of a movingstairway installation embodying the invention;

FIGURE 2 is a simplified diagrammatic representation in side elevationof the upper end of a moving stairway embodying the invention; and

FIGURE 3 is a simplified fragmentary cross-sectional view taken alongline 3 3 of FIGURE l.

For the sake of brevity, the moving stairway structure illustrated inthe drawings has been greatly simplified.

However, the moving stairway may be considered to be present daycommercial construction, as described in Patent No. 2,686,585, issuedvto S. G. Margles et al.

The moving stairway comprises an endless series of steps 10, adapted tobe moved in either direction between balustrades 12 from one to anotherlanding, each landing being generally designated 14. Each step 1t)includes a horizontally disposed tread plate 16 and a verticallydisposed curved riser 18, both secured to a pair of step yokes 20. Thesteps are driven by running gear chains 22, one on each side of thestairway.

These chains are driven by sprocket wheels 24 at the upper end of thestairway, which sprocket wheels are in turn driven by a reversibledriving machine (not shown). Each running gear chain 22 includes aplurality of chain wheels 25. Each step 10 is attached on each side to achain wheel 25 and a trailer wheel 26. The chain wheels 25 are arrangedfor rolling engagement along one pair of tracks 2S, while the trailerwheels are arranged for rolling engagement along a second pair of tracks30. The curvature of track pairs 2S and 30 is such that the steps emergein platform formation from underneath landing 14 at the entrance of thestairway, transfer to step formation on the incline and change backagain to platform formation to pass underneath landing 14 at the exitend of the stairway.

An endless handrail 32 is provided on each side of the stairway and isdriven in synchronism with the steps 10 by the reversible drivingmachine. Each handrail 32 is supported at a convenient height above thesteps by the balustrade 12 which extends the length of the stairway.

Each balustrade 12 includes a handrail guide 34 for guiding handrail 32,a deck member 35 upon which guide 34 is mounted, a skirt panel 36adjacent the side edges of steps 10, and a side panel 38 positionedintermediate skirt panel 36 and deck member 35. The aforementionedhandrail guide balustrade panels and deck member may be secured to eachother and to the building structure by any suitable means, as by screws(not shown).

The stair well wall is generally designated 40.

Operating clearance space is provided between relatively moving parts.Such clearance spaces include the space 42 provided between the sideedges of tread plate 16 of the steps 10 and skirt panel 36, which skirtpanel is positioned on either side of the steps along their entirelength of travel from entrance landing to exit landing; the space 44provided between the side edges of riser 18 of steps 10 and skirt panel36; the space 46 provided between the exterior surface of the curvedriser 18 of each step and the adjacent edge of the tread plate 16 of theadjacent step. In addition, there is the space 48 provided between theside edge of the handrail 32and the adjacent wall structure 40.

As has been previously stated, relative motion between the foregoingstairway components, between which a common space exists, is sometimesin a direction which creates a hazard for objects improperly placed intosimultaneous frictional engagement with adjacent component surfaces. Inorder to remove this hazard, the frictional forces which tend to drawpassengers, their clothing and objects carried by them into theaforementioned spaces are minimized, but without decreasing thedesirably high frictional engagement between the passenger carryingstairway components and the passengers being carried. To accomplishthis, the surfaces of non-load carrying components of such relativelymoving parts (between which the aforementioned common spaces exist) arecoated with a material which substantially reduces their coefcient offriction, while the surfaces of the load carrying components (such astread plate 16 and handrail 32) are made of a high friction,non-slippery material. In present day installations, such non-loadbearing surfaces are usually either of steel or enameled metals, havinga static coefficient of friction in the range of .15 against drypolished steel. In the subject invention their static coefficient offriction is materially reduced to substantially one-fourth that value,to the order of .04, thereby minimizing the frictional forces, actingupon a contacting object, toy the point where all hazard to that object,due to relative motion, is removed.

For example, such non-load bearing surfaces are covered, preferably butnot necessarily, with polytetrafluoroethylene, which is a fluorcarbonresin commercially available under the trademark Teflon. It willhereinafter be referred to as Teflon resin in this specification. Teflonresin has the lowest static coefficient of friction of any solidsubstance presently known, being approximately .04 for a 2O pound loadagainst polished steel, ASTM method (Du Pont booklet #IA-7756, 8-58).Its coeicient of friction is substantially independent of load, thespeed of frictionally engaged surfaces moving relative to each other andtemperature variations. It is nonsoiling and self-lubricating.

Teflon resin may be applied as a sheet attached with an adhesive or as asprayed powder which is then heated to about 700 degrees Fahrenheit toform a smooth surface. However, a preferred method of producing asatisfactory coating is to cover the surface with a colloidal suspensionof the resin in a liqueed thermosetting plastic. As the thermosettingplastic cools and solidifies, the resin rises to the surface to form asmooth, slick coating.

Coated with Teflon resin are: the surface of each skirt panel 36 whichis adjacent the steps 10 to form a substantially non-frictional surface50; the outer surface of each riser 18 to form a substantiallynon-frictional surface 52, and the surface area of building wall 40adjacent to handrail 32 to form a substantially non-frictional surface54.

Referring to FIGURES 1 and 3, while the stairway is moving in anascending direction, an object being carried upward on a tread plate 16and coming into contact with the surface 50 of an adjacent skirt panel36 (such as the overshoe of a passenger standing on the tread plate,which overshoe is improperly also placed in contact with the surface ofthe adjacent skirt panel) has frictional forces exerted on it which, dueto the relative motion between the object and the skirt panel, tend todraw that object `downward into operating clearance space 42. The resincoating forming the slippery surface 50 of skirt panel 36 minimizes suchfrictional forces to the extent that they are of insufficient magnitudeto draw an object into clearance space 42. While the stairway is movingin the descending direction, the aforementioned frictional forces are inan opposite direction and therefore tend to keep objects out ofclearance space 42.

However, while the stairway is moving in a descending direction, anobject carried by tread plate 16 and improperly coming into contact withskirt panel 36 has frictional forces exerted on it which tend to drawthat object upward into clearance space 44. Due to the substantiallynon-frictional surface 50 of skirt panel 36, such frictional forces areineffective to do so. While the stairway is ascending, the frictionalforces acting upon such a contacting object are in an oppositedirection.

At the exit end of the moving stairway in either the ascending ordescending directions as the steps change from step formation toplatform formation, relative motion in a vertical direction takes placebetween the riser 1S and the adjacent edge of tread plate 16 of theadjacent step. That is, at the exit end of an ascending stairway theriser 18 of a step moves downward relative to the adjacent edge of thetread plate 16 of the succeeding step,

while at the exit end of a descending stairway the riser 18 movesdownward relative to the adjacent edge of the tread plate 16 of thepreceding step. If, as riser 18 moves downward vertically relative tothat adjacent edge, there is in contact with its surface a fairly exibleobject of high frictional material, the frictional forces that aredeveloped tend to draw the object carried by tread plate entails 16downward into clearance space 46. The Tellen resin coating forming theouter surface 52 of each riser 18 provides a substantiallynon-frictional surface which minimizes such frictional forces to thepoint where they are insumcient in magnitude to draw an object intoclearance space 46.

While the stairway is either ascending or descending, an object (forexample, a forearm), coming into simultaneous contact with the side edgeof handrail 32. and that portion of the surface of the wall itl which isin advance of the direction of handrail travel can, if frctonallyengaged sufficiently by both relatively movingI surfaces, be caughtcrosswise between the two and fractured. Since the wall surface adjacentto the handrail is coated with Teflon resin to provide a substantiallynon-frictional surface 54, the frictional forces exerted on such anobject are minimized to the point where that object is prevented frombeing frictionally engaged sufficiently by the wall surface and injuryor damage is avoided. The object instead tends to slide along theadjoining resin coated wall surface 54.

lt may be noted that the subject arrangement effectively minimizesfrictional forces tending to draw portions of passengers, their clothingand objects carried by them into operating clearance spaces without inany way reducing the secure footing and gripping provided for thepassengers.

Optionally, polytetrafluoroethylene adulterated with an additive andcommercially sold under the trademark Rulon may be used to coat theaforementioned stairway components in lieu of Teflon TFE resin.

As many changes can be made in the above described construction and manyapparently different embodiments of this invention can be made withoutdeparting from the scope thereof, it is intended that all mattercontained in the above description or shown on the accompanying drawingsbe interpreted as illustrative only and not in a limiting sense.

What is claimed is:

1. A moving stairway comprising, an endless series of steps adapted forcarrying passengers from one landing to another in ascending anddescending directions, each of said steps including a tread portion anda riser portion and each running on tracks arranged betweenbalustrading, said tracks being arranged so that said steps emerge fromunder the landing at the stairway entrance in platform formation, changeto step formation on the incline and back to platform formation at theirexit end, said balustrading including a skirt panel adjacent the rightand left edges of said steps, characterized in that the surface of theskirt panels adjacent said step edges and the outer surface of saidriser of each step are coated with a solid material having a staticcoefficient of friction of substantially .04 for a 20 pound load againstpolished steel, ASTM method.

2. A moving stairway comprising, an endless series of steps adapted forcarrying passengers from one landing to another in ascending anddescending directions, each of said steps including a tread portion anda riser portion and each running on tracks arranged betweenbalustrading, said tracks being arranged so that said steps emerge fromunder the landing at the stairway entrance in platform formation, changeto step formation on the incline and back to platform formation at theirexit end, said balustrading including a skirt panel adjacent the rightand left edges of said steps, characterized in that the surface of theskirt panels adjacent said step edges and the outer surface of saidriser of each step are coated with a non-soiling, self-lubricatingmaterial having a static coefficient of friction of substantially .G4for a 2) pound load against polished steel, ASTM method.

3. A moving stairway comprising, an endless series of steps, eachincluding a passenger carrying portion disposed in a horizontaldirection and a riser portion disposed in a vertical direction; meansfor driving said lsteps in ascending and descending directions; a set oftracks for supporting said steps and adapted for causing said steps toemerge in platform formation at their entrance end, change to stepformation on the stairway ind eline and back to platform formation attheir exit end, whereby the passenger carrying portion of each of saidsteps moves upward vertically relative to the adjacent riser portion ofthe step adjacent it as said steps convert from step to platformformation at their exit end, characterized in that the outer surface ofeach of said riser portions is composed of polytetrailuoroethylene,whereby an object which is in simultaneous contact with the passengercarrying portion of one step and the adjacent riser portion of theadjacent step as the steps convert from step to platform formation hasfrictional forces acting upon it which are insuflicient in magnitude todraw that object downward between the two relatively moving stairwaycomponents.

4. A moving stairway comprising an endless series of steps, eachincluding a tread portion, and each running on tracks arranged betweenbalustrading, said balustrading including a skirt board adjacent theright and left edges of said steps, each of said skirt boards having itssurface contiguous to said steps composed of a continuous coating ofpolytetrafluorethylene, and each of said step tread portions having asits upper surface a material having a large coeliicient of frictionrelative to said polytetrafluoroethylene.

5. A moving stairway installation wherein are provided an endless seriesof steps adapted for carrying passengers in a stair well from onelanding to another, an endless handrail driven in synchronism with saidsteps, said stair well including a wall surface positioned adjacent saidhandrail, characterized in that said adjacent wall surface is composedof a material having a static coeiiicient of :friction of substantially.04 for a 2() pound load against polished steel, ASTM method, whereby anobject in simultaneous contact with said handrail and said adjacent wallsurface slides along said wall surface in the direction of handrailtravel.

6. A moving stairway installation wherein are provided an endless seriesof steps adapted for carrying passengers in a stairwall from one landingto another, an endless handrail driven in `synchronism with said steps,said stair well including a wall surface positioned adjacent saidhandrail, characterized in that said adjacent wall surface is composedof polytetraiiuoroethylene, whereby an object in simultaneous contactwith said handrail and said adjacent wall surface slides along said Wallsurface in the direction of handrail travel.

7. A moving stairway in which an endless series of steps run from oneplatform -to another between skirt panels, one on each side, and inwhich each step has a step riser characterized in that each skirt panelsurface facing the steps is provided with a surface ofpolytetrafluoroethylene, and in that each step riser is provided with anouter surface of polytetrailuoroethylene.

References Cited in the tile of this patent UNITED STATES PATENTS2,686,585 Margles Aug. 17, 1954 2,691,814 Tait Oct. 19, 1954 2,750,697Jacobson June 19, 1956

1. A MOVING STAIRWAY COMPRISING, AN ENDLESS SERIES OF STEPS ADAPTED FORCARRYING PASSENGERS FROM ONE LANDING TO ANOTHER IN ASCENDING ANDDESCENDING DIRECTIONS, EACH OF SAID STEPS INCLUDING A TREAD PORTION ANDA RISER PORTION AND EACH RUNNING ON TRACKS ARRANGED BETWEENBALUSTRADING, SAID TRACKS BEING ARRANGED SO THAT SAID STEPS EMERGE FROMUNDER THE LANDING AT THE STAIRWAY ENTRANCE IN PLATFORM FORMATION, CHANGETO STEP FORMATION ON THE INCLINE AND BACK TO PLATFORM FORMATION AT THEIREXIT END, SAID BALUSTRADING INCLUDING A SKIRT PANEL ADJACENT THE RIGHT